That is a surprising fact I was not aware of, and it is also very good news that the fish from some parts of it are safe to eat.
Surprise on Delta fish
Mercury levels modest in south section
By Matt Weiser - mweiser@sacbee.com
Published 12:00 am PST Tuesday, November 6, 2007
It's safe for pregnant women to eat catfish, crappie, carp and bluegill caught in the south Delta. But other fish from other places? That depends.
These are some of the initial findings from the largest study ever conducted of mercury contamination in fish from the Bay-Delta watershed, a vast region of rivers and lakes that covers 40 percent of California.
The $4.5 million study, led by the San Francisco Estuary Institute, sampled more than 2,000 fish from 22 species at 69 popular fishing spots. The goal was to help understand how far the toxic legacy of the state's mining history spread throughout the watershed and wildlife.
Mercury is a naturally occurring element. But it was broadcast in a most unnatural way by decades of intensive mining that began with the Gold Rush.
Fortune hunters used mercury to separate gold from raw ore during hard-rock and placer mining. Mercury was mined on its own for this purpose.
The state produced an estimated 230 million pounds of mercury between 1846 and 1981, about 88 percent of the nation's total. About 75 million pounds was released to the environment, and mercury continues to wash into lakes and streams from old mining sites because of natural erosion and runoff.
Fish accumulate mercury in their tissue when they feed on bugs and plants. People accumulate mercury in their flesh when they eat the fish.
At low levels, this mercury is harmless. But too much can cause birth defects in children and nervous system disorders in adults.
The surprising news, according to the study, is that fish in the southern Sacramento-San Joaquin Delta are not carting around as much mercury as researchers expected. This has allowed state health officials to loosen the consumption guidelines for certain fish species caught in the estuary.
